Animal trap including spring-engaging inertial snubber to reduce initial jaw impact

ABSTRACT

An animal trap of the leghold type having low impact force is disclosed. The means for lessening the impact force of the jaws when they close in an inertial snubber lying along the trap spring and engaged by the spring before impact of the jaws to thereby absorb excess spring energy and cause the spring travel to lag behind the jaw trap.

This application is a division of application Ser. No. 660,387 filedFeb. 23, 1976, now U.S. Pat. No. 4,065,871.

BACKGROUND OF THE INVENTION

This invention relates to animal traps and more particularly thisinvention relates to a low impact leghold type animal trap.

Leghold traps have been in use for many years in the fur trappingindustry and are wide spread in their application. Depending on the sizeof the trap, a great variety of animals can be caught, usually withoutdamage to the fur. These traps have recently been widely criticizedbecause of certain aspects which are considered by some people to beinhumane. One of the most important of the disadvantages leading to thecharges of inhumanity is the fact that when the jaws clamp shut on theleg of the animal, they do so with considerable force and inflict severepain.

Interestingly, the basic design of the leghold trap has not changed overthe years with new improvements being made generally in the triggerassembly or other components not affecting the operating principle ofthe trap. See, for example, U.S. Pat. Nos. 833,827, dated Oct. 23, 1906;1,356,775 dated Oct. 26, 1920; 1,939,190, dated Dec. 12, 1933; and3,335,517, dated Aug. 15, 1967.

Although there have been improvements to leghold traps over the years,the basic construction remains the same today as it was 100 years ago.Specifically, a pair of jaws pivotally mounted on a base plate are movedupwardly from the set position to the sprung position by spring meansurging the jaws together. As already mentioned, it has been found thatthe impact force of the jaws coming together is extremely high and, infact, unnecessarily high. In order to prove this, a technique wasdeveloped at the Laboratories of Arthur D. Little, Inc. for measuringthe forces involved in these traps and a measuring apparatus wasconstructed.

It will be recognized that the behavior of a trap cannot be expressed asa single number. As the trap closes, the geometry varies continuouslyand the impact force, therefore, varies according to the size of theobject between the jaws. Similarly, the clamping force after impactvaries with jaw opening. Plotting the force versus the jaw openingaccurately defines a trap. As will be discussed more fully hereinbelow,if means could be provided to lessen the impact forces and provide moreuniform clamping force at smaller openings of the trap, the standardleghold trap can be made more humane.

Accordingly, it is a primary object of the present invention to providea leghold type trap which operates in a more humane manner than theprior art traps.

It is another object of the present invention to provide a leghold typetrap wherein the clamping force of the jaws is materially reduced atsmaller openings.

It is yet another object of the present invention to provide a legholdtype trap wherein the impact force of the jaws is reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

This invention will be better understood and objects other than thoseset forth above will become apparent when consideration is given to thefollowing detailed description thereof. Such description makes referenceto the annexed drawings wherein:

FIG. 1 is a perspective view of a trap according to one embodiment ofthe present invention;

FIG. 2 is an end view of the trap of FIG. 1;

FIG. 3 is a perspective view of another configuration of a trapaccording to the first embodiment;

FIG. 4 is a side elevation, partially fragmented, of anotherconfiguration of a trap according to the first embodiment;

FIG. 5 is a sectional view taken along the line 5--5 of FIG. 4;

FIG. 6 is a sectional view taken along the line 6--6 of FIG. 4, with thetrap in the set position;

FIG. 7 is similar to FIG. 6 but with the trap partially closed;

FIG. 8 is similar to FIGS. 6 and 7 with the jaws in the closed position;

FIG. 9 is a perspective view of a spring and damper means according to asecond embodiment of the present invention;

FIG. 10 is a perspective view of a spring and damper means and part of atrap according to another configuration of the second embodiment of thepresent invention;

FIG. 11 is an end view, partly in section, of a prior art trap with thejaws half closed;

FIG. 12 is an end view, partially in section, of a trap according toanother embodiment of the present invention;

FIG. 13 is a curve showing calculated forces against jaw opening of aprior art trap and a trap according to the third embodiment of thepresent invention;

FIG. 14 is a curve showing the actual forces plotted against jaw openingof the prior art trap and the trap according to the third embodiment ofthe present invention;

FIG. 15 is a plan view of a trap according to still another embodimentof the present invention with the trap in the set position;

FIG. 16 is a front view of the trap of FIG. 15 with the trap in the setposition;

FIG. 17 is a perspective view of the damper means used in the trap ofFIG. 15; and

FIG. 18 is a front view of the trap of FIG. 15 in the closed position.

SUMMARY OF THE INVENTION

According to the present invention, an animal trap of the leghold typeis provided having a base, a pair of U-shaped coacting jaws swingablymounted on the base, spring means biasing the jaws to a closed position,trigger means for locking the jaws in an open position until releasedand means for reducing the impact of the jaws when they close withoutsignificantly reducing the closing speed or holding power. In oneembodiment, an inertial snubber is mounted in such a way as to absorbexcess energy from the spring immediately before impact of the jaws. Inanother embodiment, the jaws are shaped to provide an escapement and thelever or spring riding up the jaws is made to contact the escapement sothat as the jaws close a point will be reached whereat the jawsmomentarily reverse their direction thereby dissipating excess energy.In another embodiment the shape of the jaws is programmed in such a waythat the energy curve will remain fairly constant.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring first to FIG. 1, there is shown a jump trap generallydesignated by the numeral 10 which has a base 12 having elongated firstand second ears 14 and 16 at the ends thereof and a pair of jaws 18 and20. Jaws 18 and 20 each comprises a pair of substantially parallelspaced legs 22 and 24 and cross-member 26. The legs 22 and 24 terminatein laterally outwardly directed pintles 28 journaled through bores 30 inears 14 and 16. Affixed to the longitudinal base 12 is a lateralcross-piece 32. Upstanding from cross-piece 32 is a leg34 having pintles36 journaled through bores 38 in the shank 40 which is integral with thepan 42. Extending upwardly and outwardly from one end of cross-piece 32is an extension 44 carrying dog 46.

It will be seen that legs 22 are relatively straight extendingdownwardly from cross-member 26 to pintle 28. In the prior art trap legs24 would have the same configuration. The last essential member of thetrap is a spring which, in the embodiment of FIG. 1, is shown as a jumpspring 48 which is in the form of a leaf spring affixed to base 12 atthe end 50 which is in the proximity of legs 22. Spring 48 is affixed tobase 12 by any suitable means such as rivets or screws 52. Spring 48terminates at the other end portion in opening or eye 54 the shape ofwhich will be described more fully hereinbelow. It will be recognized,however, that in the prior art traps the eye 54 is generally circular sothat when the trap is set with the spring forced into a position againstbase 12 and the jaws are spread apart and held in place by pan and shankassembly 40, 42 and dog 46 (see FIG. 6), and the trap is released, theend portion of spring 48 carrying eye 54 will move rapidly upwardly andurge legs 24 into the upright and closed position. But, in thisembodiment of the present invention, it is noted that legs 24, whentogether in an upright position and viewed from the end as in FIG. 2,generally conform to an "hour glass" shape. That is, each of the legs 24has a pintle 28 and then curves outwardly for a short distance at 56,inwardly at 58, outwardly at 60, and inwardly again at 62 to where thesubstantially straight portion 64 begins. The eye 54 of spring 48 has alongitudinally extending cross-piece 66 extending between legs 24 andterminating in an upwardly extending position 68.

Thus, in use, the trap is set as already explained and when triggered byan animal, spring 48 moves upwardly with outer wall 70 of eye 54 ridingalong portion 56 of legs 24 thereby urging the jaws to a closedposition. However, when eye 54 reaches the portion 58 of legs 24, thedirection of the jaws is suddenly reversed so that they momentarilybegin to open again. But, as eye 54 reaches portion 60 of legs 24, thejaws are again urged to a closed position. This momentary opening of thejaws in the middle of their closing travel absorbs or dissipatesconsiderable energy which is essentially unusable energy in terms of thenecessary clamping force to hold an animal and diminishes the impact.The loss in closing time caused by this momentary reverse motion isnegligible. The direction of travel of jaws, therefore, is, in essence,controlled by an escapement.

Referring to FIG. 3, there is seen another configuration of a trapfalling within the definition of the first embodiment of the presentinvention already described. This trap comprises base 12 and jaws 72 and74. Each of the jaws has a leg 76 and an opposite leg 78 each journaledby means of pintles 28 into upstanding ears 80 and 82. Cross-piece 32holds the pan and shank assembly and dog (not shown). It will be seenthat legs 76 are substantially straight while legs 78 form a similarescapement to that shown in FIG. 1. Instead of a jump spring as shown inFIG. 1, the configuration of FIG. 3 shows a long spring 84 which is alsoa leaf spring. Leaf spring 84 has a stationary end 86 and a slidable end88. End portion 88 has a pair of eyes 90 and 92 separated by across-piece 94. The operation of this trap is the same as the operationof the trap of FIG. 1 with end portion 88 of spring 84 moving upwardlywhen the trap is released and urging the jaws together for the firstpart of their travel, momentarily apart, and then together again.

Referring now to FIGS. 4 through 8, there is seen another configurationof a trap according to this first embodiment of the invention. In thistrap, base 12 is provided with upstanding ears 96 and 98 into whichpintles 28 of jaws 100 and 102 are journaled. Cross-piece 32 havingupstanding ears 34 and 44 carrying pan and shank assembly 42 and 40, anddog 46, respectively, are the same as previously described.

As shown in FIG. 4, partially fragmented for ease of operation, a longspring basically similar to that shown in FIG. 3 is used having upperportion 104 and lower portion 106 which, in turn, are fixed to eyemembers 108 and 110, respectively. Eye member 110 merely contains anelongated slot to fit over base portion 112 of ear 98. Eye member 108,however, has a pair of eyes 114 and 116 (FIG. 5) to fit over earportions 118 and 120, respectively (FIGS. 5 and 6). Between eyes 114 and116 is cross-piece 122.

As can be clearly seen in FIG. 8, the configuration of legs 124 and 126of jaws 100 and 102, respectively, includes a lower foot portion 128having substantially parallel linear outer surface 130 and inner surface132. Moving upwardly from foot portion 128, there is a firstintermediate portion 134 projecting inwardly and having a curved outersurface 136 and rectilinear inner surfaces 138 and 140, which can bemore easily recognized by reference to FIG. 6. Again moving upwardly,there is second intermediate portion 142 defined by substantiallyparallel linear outer and inner surfaces 144 and 146, respectively.Finally, there is upper portion 148 which is defined at its outersurface by linear edge 150 and at its inner surface by curved surface152 which is transformed to linear surface 154, linear surface 154 beingsubstantially parrallel to linear surface 150.

For ease in understanding the operation of this trap, attention isdirected to FIGS. 6 through 8, and in particular to FIG. 7. In FIG. 6,the trap is shown in its set position with jaws 100 and 102 fully openand held in place by the locking mechanism which comprises the pan 42,shank 40, and dog 46. This, in turn, compresses the spring which is heldin position by surface 130 of legs 124 and 126 of the jaws 100 and 102.Considering FIG. 7, when the jaws are released and the spring begins tomove upwardly, member 108 moving upwardly and bearing against surface130 urges the jaws up and toward the closed position. As the member 108moves to the position shown in phantom in FIG. 7, portion 122 becomesthe operative factor and, by bearing against surfaces 138 and then 140,it reverses the direction of travel of the jaws and urges them slightlymore open to the position shown in phantom in FIG. 7. As member 108continues to rise, it bears against surface 144 to close the jaws andhold them in a closed position as shown in FIG. 8.

Thus, it will be seen that each of the traps shown in FIGS. 1 through 8,while having a slightly different configuration, operates in essentiallythe same way. It will be appreciated, also, that while these traps areshown and described by reference to particular type of spring, that is,a jump spring or a long spring, the actual type of spring is immaterialand they may be interchanged. In fact, a coil spring type trap having alever of the type shown in FIG. 15 could be used in this embodiment.

Turning to the next embodiment, attention is directed to FIG. 9 whichmerely shows a prior art type long spring 154 terminating at either endin an eye 156. This spring when used in the conventional manner ismounted essentially as shown in FIG. 3 but, of course, using theconventionally shaped jaws which will be appreciated by referring toFIG. 11 or to any of the prior art patents cited above. At this point itis important to keep in mind the basic principles underlying the variousembodiments of the instant invention. Specifically, it must beunderstood that a leghold trap must grip a captured animal's leg withsufficient force to prevent escape. A spring strong enough to providethis force, however, liberates considerable energy when the trap istriggered and most of this energy is absorbed by the animal's leg. Thus,it is important to be able to dissipate excess energy harmlessly withoutcompromising the gripping power of the spring. With this in mind, andreturning to FIG. 9, there is provided a damper or snubber generallydesignated by numeral 158 which comprises an inertia arm 160 extendingoutwardly from a crank 162 rotating in upstanding legs 164. Inoperation, the trap begins to close in the conventional manner, the jawsbeing driven together by a leaf spring, either of the long spring or thejump spring type. Before the jaws contact the animal's leg, however, thespring encounters the crank 162. The spring must turn the crank,accelerating inertia arm 160 in order to continue its own motion. Sincethe arm 160 has higher inertia than the jaws, the spring essentiallylags behind the jaws and softly clamps the same shut after they havealready closed due to their own momentum.

FIG. 10 shows another form of inertial damper or snubber. In thismodification, provision is made in ear 166 which is upstanding from base12 of the trap for inserting hook means 168 of inertial snubber 170.Again, as the spring rises, it contacts inertial snubber 170 impartingexcess energy to it and lagging behind the jaws which close gently andthen become clamped by the spring.

Before discussing the next embodiment of the instant invention, it wouldbe helpful to briefly describe certain of the factors involved in theuse of a typical leghold trap. For this purpose, a standard Victornumber 3 long spring trap was used. It will be appreciated by oneskilled in the art that the principles involved apply to any size trapof the leghold type and that this discussion by reference to a number 3trap is for illustrative purposes only. FIG. 11 shows the geometry ofthe trap jaws in the standard trap. The expression F = fR/L gives thestatic clamping force at any opening. The expression F = S tan θdescribes the relationship between the jaw angle and the spring force.In these calculations, friction was ignored, as was the minor variationin spring force, since neither factor would have much effect on thebasic relationships.

The "standard #3" curve in FIG. 13 shows the results of a series ofcalculated data points. One sees a drastic increase in force at lessthan half inch opening. This would be likely to severely injure smallanimals, while allowing larger ones to escape. Redistributing the springforce in a more reasonable distribution is shown on the second curve ofFIG. 13, marked "Modified JAW #3 Trap." This was arrived at by selectingdesired values of F as θ varied. Returning to the formula F = fR/L, Lbarely varies, and both f and R vary with θ:

    f = S tan θ

    R = K sin θ

Therefore, varying θ will produce any desired value of F.

Following the above formula, jaws were fabricated as shown in FIG. 12.In this case, jaws 172 and 174 each has a lower portion 176 having acurved outer surface denoted as "C." It will be appreciated, therefore,that as the eye of the spring moves upwardly along surface C urging thejaws closed, θ constantly changes. In the particular example, using anumber 3 trap, curved surface C was arcuate. Measurements were thentaken on an instrument measuring force in millivolts, the instrumenthaving previously being calibrated so that 1.84 millivolts was equal to1 pound. Jaw opening was plotted against force for both the standardtrap and the trap with the jaws modified as in FIG. 12. The curves areset forth in FIG. 14 it was not possible to take measurements atextremely small jaw openings because of the size of the sensor. It willbe seen, however, that the curve for the standard trap is essentially ascalculated and shown in FIG. 13 and the curve for the modified jaw trapessentially follows that predicted as in FIG. 13 and, in fact, wassomewhat more level. Clearly, therefore, the impact force of the jawsclosing, regardless of the distance between the jaws at the time ofclosing on the leg of an animal, is held relatively constant and at arelatively low level. In a sense, the jaws can be "programmed" toprovide any desired force curve.

Turning now to FIG. 15, there will be seen a leghold trap of the coilspring type. This trap is shown with two springs but this embodimentcould be used with a single coil spring of the type shown in Montgomeryet al U.S. Pat. No. 3,335,517. This trap which is generally designatedby the numeral 178 comprises a base 180 having upstanding ears 182; jaws184 comprising a pair of substantially parallel spaced legs 186 and 188terminating in laterally outwardly directed pintles 191 which arejournaled through bores in ears 182; and cross-piece 190 carrying panand shank assembly 192, with the pan partially broken away for clarityof illustration, and dog 194. A generally U-shaped spring mount 196 ismounted on cross-piece 191 and base 180 in such a way that the legs 198and 200 are aligned transversely of base 180 and equidistant fromcross-piece 191. Levers 202 and 204 are mounted to pivot on legs 198 and200, respectively, of mount 196. Levers 202 and 204 are provided withopenings 206 and 208, respectively, which correspond to the eyes 156,for example, of spring 154 shown in FIG. 9. Also mounted on legs 198 and200 are coil springs 210 and 212 which are joined at their far ends bymember 214. At the ends of the coil springs 210 and 212 closest to base180, end portion 216 and 218 is fixed to the underside of lever 202 and204, respectively, so that the levers are normally biased in an upwardposition as shown in FIG. 18. As shown in FIG. 15, on the other hand,the trap is in the set position and the levers are down and the jawswide open.

To this point, the description of the trap of FIGS. 15 through 18 hasbeen a description of a conventional coil spring leghold trap. But,according to the last embodiment of the present invention, a pair ofinertial snubbers or dampers is provided which relies on the mass of thetrap itself to provide the inertial damping. The inertial snubber isshown in FIG. 17 and is generally designated by the numeral 220. Itcomprises a crank portion 222 and an arm portion 224. As will be seenfrom FIG. 15, snubber 220 is mounted in such a way that crank 222 rideson lever 202 or 204 and is mounted to pivot about the axis provided bymembers 198 and 200. Arm 224, when the trap is in the set position laysflat on the ground with the weight of the trap itself on top of thesame. This can be easily seen in FIG. 16.

Turning to FIG. 18, it will be seen that when the trap is sprung, levers202 and 204 are urged upwardly in the direction shown by arrows A bysprings 210 and 212 thereby urging jaws 184 together. At the same time,however, cranks 222 are contacted by levers 202 and 204 and caused torotate about pivots 198 and 200, respectively. As cranks 222 rotate,arms 224 move in the direction shown by the arrows labelled B. Since thetrap 178 is resting on arms 224, when arms 224 are caused to move asshown by arrows B, the trap itself is displaced upwardly. The mass ofthe trap 178 causes an inertial dampening of levers 202 and 204 whichthen lag behind the closing of the jaws 184. Jaws 184 close gently onthe animal's leg and then are tightly clamped by levers 202 and 204. Anadditional advantage of this action is that the upward movement of thecomplete trap will cause the jaws to close higher up on the animal's legthereby creating a more positive grip as well as a less painful grip.Additionally, if the animal pulls its leg away from the trap when it isstartled, the trap, in essence, follows this action and still grips theanimal's leg.

While this invention has been particularly shown and described withreference to preferred embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the spirit and scope of theinvention.

What is claimed is:
 1. In an animal trap of the leghold type having abase, a pair of U-shaped coacting jaws swingably mounted on said base,spring means biasing said jaws to a closed position, and trigger meansfor locking said jaws in an open position until released, theimprovement comprising means for reducing the impact of said jaws whenthey close without significantly reducing the closing speed or holdingpower, said base being elongated and having upstanding first and secondears at the ends thereof; said jaws each comprising a pair ofsubstantially parallel spaced legs and a cross member, said legsterminating in laterally outwardly directed pintles journalled throughbores in said ears; said spring means being a leaf spring and comprisingan eye at one end thereof; said eye encircling one leg of each jaw sothat when said jaws are in the open position and said spring is releasedthe eye thereof rides up said one leg of each jaw to thereby close saidjaws, said impact reducing means comprising an inertial snubberpivotally mounted in a bore in one of said ears and lying longitudinallyalong said spring to be operatively engaged by said spring before impactof said jaws to thereby absorb excess spring energy and cause the springtravel to lag behind the jaw travel.
 2. The improvement of claim 1,wherein said spring is a U-shaped spring.